Large Reef Reef Predators, Barracuda and Trevally

Video do giant trevally eat humans

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Black tip reef sharks and white tip reef sharks are commonly seen at reefs. There have been few reports of human attacks. Scuba divers tend to seek them out rather than avoid them. See Sharks

There are many species of predator in the reef. Sometimes they prey on the smallest of fish and it is hard to think of them as predators. Squirrel fish are predators that spend much of the day in reef crevasses. Trevallies, or jacks are medium-size predators that travel in schools. Reef skimmers and snappers have piranha-like teeth.

Several species of fish are often seen in the company of large predators. Pilot fish are small- to medium size fish with black stripes are that are often swim with fish such as sharks and rays. The large fish help the pilot fish by protecting them from potential predators and the pilot fish return the favor by feeding on parasites on the sharks.

Remoras use their suckers to hitch rides on sharks, whales, turtles, rays, dolphins almost any fish or sea mammal that is large enough to carry them. The they have a sucking disk under their head The sucker allows the fish to save energy. It is not used to suck blood like a lamprey, its is merely a fastening devise Its host provided with transport and gill venilable and protection from predators and food scraps. In return the remora cleans off parasites from its host’s skin.

Related Articles: Groupers: Characteristics, Behavior and Big Species ; Groupers in the Atlantic, Caribbean and Gulf of Mexico ; Reef Sharks: Blacktip, Whitetip and Grey Reef Sharks ; Lemon Sharks: Characteristics, Behavior, Feeding, Mating ; Nurse Sharks: Characteristics, Behavior, Feeding, Mating, Attacks ; CORAL REEFS ; CORAL REEF LIFE REEF FISH

See Sharks

Websites and Resources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Fishbase ; Encyclopedia of Life ; Smithsonian Oceans Portal ; Woods Hole Oceanographic Institute ; Cousteau Society ; Monterey Bay Aquarium ; MarineBio

Grunts, Hawkfish, Snappers and Jacks

Spanish grunts, snappers, porkfish and French grunts hunt the reef alone looking for crustaceans and small fish. Spanish grunts sometimes feed on sea urchins, whose spines leave behind a purple stain on the grunts’s face.[Source: Walter A. Stark II, National Geographic. December 1972 ╆]

Bluestriped grunts sometimes approach each other with their mouths wide open, looking as if they about to kiss or swallow each others face. No one is sure why these foot-long fish do this although scientist speculate it is a male territorial thing.╆

The 35 species of hawkfish are found in tropical waters and tend to lie on the sea bottom around coral and rocky reefs, waiting for prey come by, snatching them when they do. They feed mainly on crustaceans and small fish. If they feel threatened they use their pectoral fins to lodge themselves in a crevice making it difficult for predators to get at them and extract them. The fish tend to live on their own. Sometimes males form harems in their territory.

Jacks swim in schools during the day for protection against barracuda and other predators and separate at night to hunt smaller fish. Sometimes they rotate in near perfect gyres when they school.

Red snappers can are among the more aggressive predators on the reef, The have need sharp teeth and a voracious hunger and reach lengths of 70 centimeters. unless provoked. Red snapper is a name used to describe many species of fish served up at restaurants. They are not necessarily the ones you find at the reef. The American red snapper reaches a weigh of 35 pounds but is usually eaten when it weighs 10 pounds. Adults live around rocky reefs. Juveniles along sandy or muddy bottoms. They are often caught by dredges on shrimp trawlers.


Groupers are generally solitary predators. Like other predatory fish such as barracuda, they are most active at dawn and dusk. Some prefer deep waters. Others are found in warm, shallow coastal waters, often in coral reefs and sometimes in estuaries. Groupers have been described as patient hunters because they like to lurk in caves or crevices and wait for a crustacean or slow-moving fish to pass their way and then lunge, open their large mouth and suck in the prey. Coral groupers catch fish with the suction created when it opens its huge mouth.

Groupers live for a long time and reproduce for short periods. Some species gather in large groups to spawn. Groupers tend to be fond of spiny lobster and also frequently eat crabs, small fish and juvenile sea turtle. When they are young they are fed on by other predators but if they manage to make it to adulthood the only real threat they face comes from humans.

There are several species of grouper. The giant grouper, which lives in the Indian Ocean and the western and central Pacific, is one of the largest species and is known to occasionally feed on small sharks. Other large species include the jewfish and goliath grouper. Many kinds of groupers can change their color to match their surrounding. Some species register victory or defeat by changing color.

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Trevallies are large marine fish in the Carangidae jack family that often travel in schools. They are is classified within the genus Caranx, that includes of a number of groups known as jacks. Caranx itself is part of the larger jack and horse mackerel family Carangidae, which in turn is part of the order Carangiformes. [Source: Wikipedia]

Trevallies are relatively big fish with a wide body. They have ovate, moderately compressed bodies with the dorsal profile more convex than the ventral profile, particularly anteriorly. The dorsal fin of the giant trevally is in two parts, the first consisting of eight spines and the second of one spine followed by 18 to 21 soft rays. The anal fin consists of two anteriorly detached spines followed by one spine and 15 to 17 soft rays. The pelvic fins contain 1 spine and 19 to 21 soft rays. The caudal fin is strongly forked, and the pectoral fins are falcate, being longer than the length of the head. The lateral line has a pronounced and moderately long anterior arch, with the curved section intersecting the straight section below the lobe of the second dorsal fin.

Giant Trevally

The giant trevally (Caranx ignobilis), also known as the lowly trevally, barrier trevally, giant kingfish or ulua, It is found throughout the tropical waters of the Indo-Pacific region, from South Africa in the west to Hawaii in the east, Japan in the north and Australia in the south.[Source: Wikipedia]

The giant trevally is distinguished by its steep head profile and strong tail scutes. It is normally a silvery colour with occasional dark spots. Males are sometimes black once they mature. The largest fish in the Caranx genus, it reaches lengths of 170 centimeters (67 inches) and a weight of 80 kilograms (176 pounds). The fish inhabits a wide range of marine environments, from estuaries, shallow bays and lagoons as a juvenile to deeper reefs, offshore atolls and large embayments as adults. Juveniles tend to live in waters of very low salinity such as coastal lakes and upper reaches of rivers, and tend to prefer turbid waters.

The giant trevally is an apex predator in most of its habitats, and is known to hunt individually and in schools. It mainly eats fish of various kinds but also preys on crustaceans, cephalopods (octopus, squid and cuttlefish) and molluscs, making up a significant portion of its diet in some regions. Among its interesting hunting strategies are following monk seals to pick off escaping prey and using sharks to ambush prey.

Footage shown in the 2017 documentary series “Blue Planet II”, shot in the Farquhar Atoll in the Seychelles, shows a group of approximately 50 giant trevally hunting fledgling terns learning to fly and crash landing and the fish taking birds, including adults, that flew low enough over the water for the fish to grab them.

The giant trevally reproduces in the warmer months, with peaks differing by region. Spawning occurs at specific stages of the lunar cycle, when large schools congregate to spawn over reefs and bays. The fish grows relatively fast, reaching sexual maturity at a length of around 60 centimeters at three years of age.

The giant trevally is both an important commercial fish and sport fish, with 4,000-10,000 tonnes of the fish caught in the the Asian region. The taste of the fish varies from poor to excellent depending on the source. Despite having relatively low numbers in some places,the fish has been designated as a species of least concern by the International Union for Conservation of Nature (IUCN).

Bluefin Trevally

The bluefin trevally(Caranx melampygus) is also known as the bluefin jack, bluefin kingfish, bluefinned crevalle, blue ulua, omilu, and spotted trevally. It is found throughout tropical waters of the Indian and Pacific Oceans, ranging from Eastern Africa in the west to Central America in the east, Japan in the north and Australia in the south. The bluefin trevally is sought after by both commercial and recreational fishermen. It has been designated as a species of least concern by the IUCN.[Source: Wikipedia]

The bluefin trevally reaches the length of 117 centimeters (46 inches) and a weight of 43.5 kilograms (96 pounds), however ones over 80 centimeters (31 inches) are rare. It is easily recognized by its electric blue fins, tapered snout and numerous blue and black spots on their sides and inhabits both inshore environments such as bays, lagoons and shallow reefs, as well as deeper offshore reefs, atolls and bomboras. Juveniles prefer shallower, protected waters, even entering estuaries for short periods in some places.

The bluefin trevally is a powerful predatory fish that mainly eats fish but also consumes cephalopods and crustaceans as an adult. It uses a wide array of hunting techniques ranging from reef ambushes, midwater attacks and foraging on prey missed by larger species (See Above). The bluefin trevally reproduces at different periods throughout its range, and reaches sexual maturity at 30-40 centimeters in length and around two years of age. It is a multiple spawner, capable of reproducing up to 8 times per year, releasing up to 6 million eggs per year in captivity. The fish reaches 19.4 centimeters in its first year, 34 in the second and 45.6 centimeters in the third year.

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Trevally’s Extraordinary Hunting Skills

Trevallies are fast swimmers and feed mainly on fish. Two studies of adult giant trevallies in Hawaii found fish to be the main food type, making up over 95 percent of the trevally’s stomach contents. Most of the fish were small reef-dwelling wrasses (Labridae), goatfishes (Mullidae), parrotfish (Scaridae) and bigeyes (Priacanthidae). Trevallies seem to have a preference for fish of a specific size, which depends on their own length and age.

Trevally displays a wide and innovative array of hunting techniques, ranging from midwater attacks to ambushs to working with other species of fish. fish. The bluefin trevally hunts during the day, particularly at dawn and dusk as a solitary individual and in groups of up to 20 members. Most prefer the lone wolf approach. In groups, they fish rush their schools of prey fish, breaking up the school and picking off isolated individuals. Giant trevallies in captivity have been observed doing the same thing. In some instances, only one individual in a group attacks the prey school. When hunting in midwater, trevally swim both against and with the current but mostly with it,

The stealthy barcheek trevally sometimes hides behind large non-threatening fish such as triggerfish and darts out from its hiding place to snag prey unafraid of the clown triggerfish. When in ambush attack mode the blue trevally change colour to a dark pigmentation state and hides behind large coral lumps close to where the aggregations (often spawning reef fish) occur. Once the prey is close enough to the hiding spot, the fish ram the base of the school, before chasing down individual fish. Bluefin trevally also enter lagoons as the tide rises to hunt small baitfish in the shallow confines, leaving as the tide falls. The species is also known to follow large rays, sharks and other foraging fish such as goatfish and wrasse around sandy substrates, waiting to pounce on any disturbed crustaceans or fish which are flushed out by the larger fish.


Barracuda are strong, fast-moving predators that have few enemies other than large sharks. They have a long muscular body, a large head, long snout, a forward-projecting jaw and scary-looking spike-like teeth. They are found in all the world’s oceans, although they seem to be biggest and most plentiful in the Caribbean.

Barracuda can reach lengths of two meters and weigh up to 50 kilograms although usually they are around one meter or a little more in length. They tend to stay close to the surface in warm waters and are rarely seen in cold water or below a depth of 100 meters. Juveniles are sometimes found in large groups but most of the time adults are found in small groups or alone. Many fisherman used to think that barracudas were closely related to pikes because of the similarity in their body form.

Barracuda look menacing and are very curious. They often follow divers around, but they rarely attack anyone. Fish don’t have it so easy. When a barracuda clamps its jaws around a snapper divers have said they heard the crunching of bone under water.

If you go snorkeling or diving in waters with barracuda, don’t wear glimmering metal objects like jewelry or a watch; barracuda are attracted to these things and you. Also don’t provoke the, A barracuda bite can cause serious injury. often her stories about women wearing anklets whose feet were attacked when they dangled in the water. Such attacks often occur in murky eater when the barracuda mistakes the jewelry for a fish.

Barracuda’s long body and sharp teeth are adapted for swimming fast for short periods of time and biting. attacks by lying relatively motionless and then suddenly lunging forward. To grab prey. They are most active at dawn and dusk. Barracudas catch prey by circling round a school and choosing a moment when they might be confused, especially around dusk to dawn and biting a skalsing and hoping to snag a confused fish

Some people like the taste of Great barracuda meat but ciguaterra is an issue with the fish. Large individuals in particular can cause ciguatera poisoning,a serious illness that can result in some severe nausea and other nasty symptoms, sometimes even death. Very little barracuda meat is eaten in the United States.

The barracuda belong to the genus Sphyraena, which contains 29 species. Among them are the Sharpfin barracuda, Arabian barracuda, Pacific barracuda, Great barracuda, Northern sennet, Yellowstripe barracuda, Mexican barracuda, Yellowtail barracuda, Bigeye barracuda, Pelican barracuda, Japanese barracuda, Australian barracuda, Red barracuda, Sawtooth barracuda, European barracuda and Yellowmouth barracuda,

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Great Barracuda

Great barracuda (Scientific name: Sphyraena barracuda) have an average lifespan in captivity is 14 years. They are found in tropical waters in the Indian Ocean, Atlantic Ocean and western Pacific Ocean. They have been found in the Red Sea and as far north as Massachusetts in the Atlantic. They are often seen in the Caribbean Sea and prefer clear water with temperatures between 23 and 28 degrees C (74 and 82 degrees F), although they have been found in much colder water. Few people like to fish them although they can put up a good fight. Great barracudas can be dangerous and have attacked snorkelers and divers.[Source: Brianne Fuller, Animal Diversity Web (ADW) /=]

You can typically find great barracudas in reefs or other coastal areas. Adult live in and around the edges of coral reefs and tend to avoid brackish water unless they are preparing to spawn. Post-larvae live on the margins of and in the estuaries where they are protected. When they get large enough to protect themselves, they head to open ocean and later to the margins of the coral reefs./=

Great barracuda at all ages eat other fish. Their large teeth are quite useful for snagging prey. They hunt using both sit-in-wait and active predator styles. As juveniles, they fish compete with needlefishes and small snapper for food, which consists of killifishes, herrings, sardines, gobies, silversides, anchovies small mullets, and lizardfishes. As the barracuda get older and bigger, they may compete with larger fish like mackerel, or even dolphins, depending on their habitat. Then great barracuda feed on both bottom-dwelling species as well as species of the higher water column, They been observed herding schools of fish into shallow water and guarding them and eating them when their last meal is digested and they are hungry again

Great Barracuda Characteristics and Behavior

Great barracuda are large, long fish with two widely separate dorsal fins. They can reach a length of around two meters. Their average weight is 40 kilograms (88.11 pounds). According to Animal Diversity Web: They have large scales and a pointed head with a large mouth and long knife-like teeth. Great barracuda have a large gape, which allows them to feed on very large fish by chopping them in half. Their lower jaw project forward more than the upper one and this is helpful in biting. Their bodies are grayish brown above and silvery below.They often have dark ink-like spots that are arranged in no pattern on their sides. The young have dark crossbars on their backs and blotches on their sides. The young also have a soft dorsal fin and the anal and caudal fins can be blackish. Males and females are roughly the same in size, shape and coloration. [Source: Brianne Fuller, Animal Diversity Web (ADW) /=]

Great barracuda sense using touch and chemicals usually detected with smell. They tend to be solitary fish as adults, especially at night. But juveniles and adults are often observed traveling in schools during the day. Groups of hundreds and even thousands of great barracudas have been observed but are rarely seen. They kill compulsively and destroy more than they eat. Most often, great barracudas attack humans only when provoked. /=

Great Barracuda Mating

null barracuda Great barracuda oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups). Reproduction is external, meaning the male’s sperm fertilizes the female’s egg outside her body. On average females reach sexual or reproductive maturity at age 1460 days while males do so in 730 days. [Source: Brianne Fuller, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: It is still unclear about the timing and location of spawning of great barracuda. Some research reports that they spawn in the spring. Others claim that they spawn in association with particular phases of the moon. Still others claim that great barracudas spawn throughout the year with the exception of the winter months when it is cooler. It may be that great barracudas show different spawning patterns in different areas of the world. /=

Great barracuda do not care for their fertilized eggs. They are left to drift out into the ocean and eventually take form. When the fish spawn they enter shallow waters such as estuaries. The larvae hatches and seeks shallow weedy areas on the margins of clear-water estuaries. When the larvae reach a length of about 80 millimeters they move to the deeper waters of adjacent reed beds. At about 300 millimeters they move to open waters and eventually they move out of the estuaries completely at about 500 millimeters in length.

Image Sources: Wikimedia Commons; YouTube, Animal Diversity Web, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2024

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